The present invention relates to flashlamps, and more particularly to microwave assisted flashlamps. Even more particularly, the present invention relates to microwave assisted flashlamps wherein microwaves are used to manipulate dopant levels, and initial and boundary conditions of the flashlamp to advantageously change the emission spectra of the flashlamps.
Flashlamps have heretofore been used in photocopying, curing of UV coatings, laser applications, photo typesetting, visual beacons, and more recently for the destruction of biological organisms. See, for example, U.S. Pat. No. 4,871,559 (Dunn, et al.) for Preservation of Foodstuffs; U.S. Pat. No. 4,910,942 (Dunn, et al.) for Methods for Aseptic Packaging of Medical Device; and U.S. Pat. No. 5,034,235 (Dunn, et al.) for Methods for Preservation of Foodstuffs, all of which are hereby incorporated by reference as if set forth in their entirety.
These applications of flashlamps are limited by the spectral emission characteristics of commercially available flashlamps, which produce a large portion of their emission in the visible and infrared.
A flashlamp is an arc lamp that operates in a pulsed mode, and that is capable of converting stored electrical energy into intense bursts of energy, at typically about 300 kW per cubic centimeter. Irradiated energy from a flashlamp is typically within a spectrum that covers ultraviolet, visible, and infrared light regions. Spectral output is mostly limited to black body-like spectra of Xenon and Krypton gases. The distribution of output between ultraviolet, visible, and infrared light can be altered to a limited extent by varying effective temperature of an irradiating gas. However, this ability to vary the distribution of output is limited, and spectral control, such as in moderate pressure gas discharge lamps, is not available in heretofore known commercially available systems.
Pulsed RF electrodeless lamps have been studied as a means of utilizing dopant atoms in a pulsed discharge by MITRE. (See F. W. Perkins "Blue Green Lasers and Electrodeless Flash Lamps", MITRE Corporation, JHSR-83-101, August, 1983.) The discharges generated by the pulsed RF electrodeless lamps studied by MITRE had limitations due to the interception of RF radiation coils, and were also limited in power density.
Pulsed Microwave lamps have been operated experimentally at levels of 10.4 megawatts per cubic centimeter in KRF laser experiments. The pulsed microwave technology heretofore available is expensive, as compared to electrode flashlamps or electrodeless microwave energized bulbs. (See V. A. Vaulin, et al., "Krypton Fluoride Laser Excited by High Power Nanosecond Microwave Radiation, "Sov. J. Quantum Electron. 18 (11), (November, 1988.)
Electrodeless microwave energized bulbs offer a wide variety of spectra choices, because steady state electrodeless microwave energized bulbs can be produced with dopant atoms such as mercury, iron and copper. (See, for example, U.S. Pat. Nos. 4,042,850; 3,872,349; 3,911,318; 4,887,008; 4,749,915; 4,641,033; 4,887,192; 4,902,935; 4,894,592; 4,507,587; 4,954,755; and 5,051,663.) Commercially available electrodeless microwave energized lamps are limited in power density, as compared to flashlamps, i.e., are limited to about 0.09 to 3 kW per cubic centimeter.
Sulfur and selenium fills for electrodeless and electrode lamps are discussed in U.S. Pat. No. 5,404,076 (Dolan, et al.) and U.S. Pat. No. 5,606,220 (Dolan, et al.), but there is no suggestion that RF or microwave energy be applied to the electrode lamps.
Unlike the above-described approaches, the present invention achieves both high pulsed power levels and dopant handling and/or spectral changing characteristics.